Pressure transmitter installation in a process line of a process facility

ABSTRACT

A flow control unit having a housing with a valve chamber. The valve chamber has an inlet and an outlet. The inlet of the valve chamber is placed in communication with the process circuit. A valve member is carried within the valve chamber. The valve member has an open position for allowing flow from the inlet of the valve chamber to the outlet of the valve chamber, and a closed position for preventing flow through the valve chamber. A pressure cell is disposed adjacent the outlet of the valve chamber. A closed pressure circuit is defined from the valve inlet, the valve chamber, and the valve outlet. A pressure sensor is disposed in the pressure cell and traverses the circuit at the outlet for measuring the pressure of the process circuit communicated through the closed pressure circuit when the valve member is in the open position.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a pressure transducer assemblyfor measuring the pressure in a process circuit of a process plant.

[0003] 2. Description of Related Art

[0004] In process plants, such as chemical and refining plants, pressuretransducers installed on the site are used as field instruments tomeasure fluid pressure. Pressure transducers are used for example tomeasure the fluid pressure and to detect the extent that the processcircuit is full of fluid. Measuring diaphragms with differentialpressure transducers are frequently used to ascertain the fluid flow inthe circuit.

[0005] A known pressure transducer assembly of this type for use on aprocess circuit of a process plant is disclosed in German patent DE 19921 172 C1. The pressure transducer assembly comprises a pressuretransducer carried on a valve block. A fluid line is disposed between aprocess circuit and the valve block. A flow control unit in the form ofa stop valve is installed between the process circuit and the valveblock. A first flange connection is provided between the connection onthe process circuit and fluid line. A second flange connection isprovided between the valve block of the pressure transducer and thefluid line. The fluid line runs through the stop valve upstream of thevalve block. The stop valve is connected to the process circuit at aninput side downstream of the process circuit flange connection whichoperates as a first portion of the fluid line. The stop valve has achamber in which a movable valve member is received. It can be movedfrom a flow-through position, in which a flow-through connection isestablished from the input side of the stop valve before to the valveblock of the pressure transducer following the valve member of the stopvalve, and into a closing position in which the flow-through connectionis closed. Along the fluid line in the pressure transducer, a pressurecell with a pressure sensor is installed, whereby the pressure sensor isconnected to an electronic measuring system for indicating the pressureof the process circuit when fluid is directed through the stop valve andinto the valve block.

[0006] In order to reduce the cost of the installation, this typicalpressure transducer assembly is connected directly into the processcircuit whereby the short and stable interconnected components of thepressure transducer assembly take on a support function. The stop valve,which may be, for example, in the form of a ball valve or tap cock, isconnected to numerous valve blocks on the downstream side to whichtransducer bodies, and with them the measuring cells contained thereinand the housing of the electronic measuring systems are in turnconnected. In a differential pressure transducer assembly of this type,and also known from DE 199 21 172 C1, two parallel fluid pressuremeasuring circuits, each with an associated stop valve and each with adownstream valve block to a differential pressure transducer areinstalled.

[0007] This known and expensive connection of one stop valve for eachvalve block, linked one after the other in a sequential manner in acircuit is necessary to make it possible to carry out manipulations on agiven pressure transducer, such as for maintenance or transducerreplacement, as well as to manage the pressure conditions downstream ofa locked stop valve, as well as media-caused problems such as in thepresence of toxic media. In addition, selected stop valves can be openedin dead spaces in order to achieve targeted pressure reduction in aknown manner after the closing of an upstream stop valve when processpressure still prevails. However, these dead spaces downstream of theclosed stop valve may also cause problems, for example, with respect toa temperature expansion or sterility of media residues remainingtherein, so that such dead spaces may possibly prove costly to rinse outand must be sterilized e.g. for food production.

[0008] Accordingly, it is an object of the present invention to furtherdevelop a pressure transducer assembly of this type in such manner thatthe installation becomes more economical and compact and so that theabove-mentioned disadvantages may not occur or at least be reduced to agreat extent.

SUMMARY OF THE INVENTION

[0009] The above objectives are accomplished according to the presentinvention by providing a pressure transducer assembly for measuring thepressure in a process circuit of a process plant comprising a flowcontrol unit having a housing with a valve chamber. The valve chamberhas an inlet and an outlet. The inlet of the valve chamber is placed incommunication with the process circuit. A valve member is carried withinthe valve chamber. The valve member has an open position for allowingflow from the inlet of the valve chamber to the outlet of the valvechamber, and a closed position for preventing flow through the valvechamber. A pressure cell is disposed adjacent the outlet of the valvechamber. A closed pressure circuit is defined from the valve inlet, thevalve chamber, and the valve outlet. A pressure sensor is disposed inthe pressure cell and traverses the circuit at the outlet for measuringthe pressure of the process circuit communicated through the closedpressure circuit when the valve member is in the open position.Accordingly, additional valves are omitted and the pressure cell islocated directly behind the valve member at the valve chamber outlet tominimize dead space directly following the valve member.

[0010] Since the pressure cell is positioned directly downstream of thevalve member and valve outlet, it is essentially integrated into theflow control unit and only one valve member is used per closed pressurecircuit. Thus, the pressure transducer assembly can be produced moreeconomically thanks to the omission of additional stop valves/flowcontrol units and valve blocks carrying the pressure transducer.Furthermore the overall assembly is light in weight, so that when it ismounted directly on a process circuit, only a relatively low supportingforce is required. This also applies when the process circuit isconnected via a process circuit connection flange to the processcircuit.

[0011] Due to the direct integration of the pressure cell into the flowcontrol unit, dead spaces can be minimized to such an extent that theycan be disregarded without any problem for the functioning of thepressure transducer assembly. As a result, a valve block on thedownstream side of a stop valve can be dispensed, and the problems andnecessary work associated with the conventional, relatively large deadspaces are eliminated and thus do not occur. Such minimization or alsoomission of dead spaces is especially advantageous with toxic materialsand with media that must be kept sterile. Other required rinsing andsterilization operations can be advantageously omitted. The problems oftemperature expansion in dead spaces is also eliminated.

[0012] So-called known ball valves or tap cocks can be used in the flowcontrol unit as they are well suited for the integration of the pressurecells immediately after the valve member.

[0013] In a preferred embodiment, the pressure cell is included in adetachable cover element mounted to the housing over the outlet of thevalve chamber. Thereby the pressure sensor can simply be inserted intothe pressure cell and can be mounted, being also easily accessible forpossible maintenance or replacement after detaching the cover element.

[0014] A conventional pressure membrane installed directly andtransversely after the valve member can be used as the pressure sensorin order to minimize dead spaces. Deformation of and/or strain of thepressure membrane by an applied process pressure is converted into anelectric measurement signal and is processed further in the connectedelectronic measuring system. The electronic measuring system isadvantageously contained in an electronics housing connected to the flowcontrol unit to constitute a compact unit. Preferably, the electronicshousing is carried by the detachable cover, so that the electronicshousing constitutes one unit for assembly together with the measuringelectronics, the covering element and a connected or connectablepressure sensor.

[0015] The above-described pressure transducer assembly can also bedesigned as a differential pressure transducer assembly with the samecharacteristics and measures as detailed above. For this purpose, twoclosed pressure circuits are provided, each with an associated flowcontrol unit and each with a valve member in at least one housing of aflow control unit. A differential pressure cell is integrated with adifferential pressure sensor and disposed between two closed pressurecircuits directed towards each other with minimized dead space followingthe valve members and leading to the pressure cell, whereby each of thetwo closed pressure circuits leads to one side of the differentialpressure sensor. Thereby the advantages described earlier regarding apressure transducer assembly also apply to the differential pressuretransducer assembly.

[0016] A circuit layout that is advantageous for compact design isachieved with the two closed pressure circuits running parallel to eachother from the process circuit in at least one housing of a flow controlunit. The closed pressure circuits starting at a connection flange onthe process circuit are brought together in an arc with intercalation ofthe respective valve members, each ending at one side of thedifferential pressure sensor at the central differential pressure cell.

[0017] Simple assembly and possible subsequent easy access to thedifferential pressure sensor is achieved wherein the housings of twoseparate flow control units are provided, and wherein the housings areadapted for adjoining to each other in the region of the centraldifferential pressure cell and capable of being separated from eachother.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The construction designed to carry out the invention willhereinafter be described, together with other features thereof. Theinvention will be more readily understood from a reading of thefollowing specification and by reference to the accompanying drawingsforming a part thereof, wherein an example of the invention is shown andwherein:

[0019]FIG. 1 shows a schematic section through a pressure transducerassembly on a process circuit of a process plant, and

[0020]FIG. 2 shows a schematic cross-section through a pressuretransducer assembly designed as a differential pressure transducerassembly on a process circuit of a process installation.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0021] With reference to the drawings, the invention will now bedescribed in more detail. FIG. 1 schematically shows a cross-sectionthrough a pressure transducer assembly 1 on a process circuit 2, shownhere only schematically and by broken lines, of a process plant.

[0022] This pressure transducer assembly comprises in this case e.g. aprocess circuit connection flange 3 on the side of the process circuit,followed by a closed pressure circuit 4 formed in housing 7 of flowcontrol unit 5 by valve chamber 8, inlet 4 a, and outlet 15. A valvemember 9, shown by way of example as a ball valve is installed in thepressure circuit 4 and is in fluid communication via flow control unitconnection flange 6 to the process circuit at connection flange 3. Theball valve is carried within valve chamber 8 in housing 7. Preferably,valve member 9 includes a passageway forming a flow-through opening 10that that can be selectively positioned to allow flow through closedprocess circuit 4. The valve member 9 is sealed against housing 7 invalve chamber 8 by means of seals 11, 12.

[0023] As can furthermore be seen in FIG. 1, flow control unit 5 furtherincludes an actuating lever 13 connected to the ball valve member 9 insuch a manner that the latter can be moved from an open flow-throughposition 14 shown in FIG. 1 in which a flow through connection isestablished from inlet 4 a of valve chamber 8 to outlet 15 downstream ofvalve member 9, into a closed position indicated in FIG. 1 by arrow 16but not shown, in which the flow-through connection is accordinglyclosed.

[0024] It can furthermore be seen in FIG. 1 that a pressure cell 17,installed in the closed pressure circuit 4, is integrated into housing 7at outlet 15 of valve chamber 8 with minimum dead space directlyfollowing ball-shaped valve member 9.

[0025] The end of outlet 15 is made in the form of a pressure cell andis produced by means of a detachable cover element 18, whereby apressure sensor in form of a pressure membrane 19, is located directlyand transversely downstream of the flow-through opening 10 of valvemember 9.

[0026] The pressure membrane 19 is connected in the usual manner via acorresponding circuit 20 to an electronic measuring system 22 containedin an electronics housing 21 and shown here only schematically.

[0027] The electronics housing 21 is furthermore connected to thedetachable cover element 18 of the measuring cell, and this is alsoshown schematically only for purposes of an example.

[0028]FIG. 2 shows an alternative embodiment in which a pressuretransducer assembly is designed as a differential pressure transducerassembly 23. A process circuit 24 is here connected via two processcircuit connection flanges 25, 26, also shown merely schematically andby broken lines as is the process circuit 24, to a flow controlconnection flange 27, 28 of each of two downstream closed pressurecircuits 29, 30.

[0029] Each closed pressure circuit 29, 30 is assigned a flow controlunit 31, 32, each with a valve member 33, 34 in the form of a ballvalve, for example, in a valve chamber of housing 35, 36 of the flowcontrol unit.

[0030] As can further be seen in FIG. 2, the two closed pressurecircuits 29, 30 are parallel, starting at the flow control unitconnection flange 27, 28 and are then brought towards each other withintercalation of the ball shaped valve member 33, 34, whereby adifferential pressure cell 37 is integrated with a pressure membrane 38in form of a differential pressure sensor into an outlet 41 of the twoclosed pressure circuits 29, 30, with minimum dead space downstream ofthe two ball-shaped valve members 33, 34 of the flow control units 31,32. In this case the two closed pressure circuits 29, 30 end on eitherside of the pressure membrane 38 at the central differential pressurecell 37.

[0031] The two flow control unit housings 35, 36 adjoin each other herein the region of the differential pressure cell 37 and are connected ina detachable manner to each other. Here too, the pressure membrane 38 iscoupled to an electronic measuring system contained in an electronicshousing 40 that can be connected to the housings 35, 36, and this isalso shown schematically in FIG. 2 for purposed of example.

[0032] While a preferred embodiment of the invention has been describedusing specific terms, such description is for illustrative purposesonly, and it is to be

What is claimed is:
 1. A pressure transducer assembly for measuring thepressure in a process circuit of a process plant, said pressuretransducer comprising: a flow control unit having a housing with a valvechamber, said valve chamber having an inlet and an outlet; said inlet ofsaid valve chamber in communication with said process circuit; a valvemember carried within said valve chamber, said valve member having anopen position for allowing flow from said inlet of said valve chamber tosaid outlet of said valve chamber, and a closed position for preventingflow through said valve chamber; a pressure cell disposed adjacent saidoutlet of said valve chamber; a closed pressure circuit defined from thevalve inlet, said valve chamber, and the valve outlet; a pressure sensordisposed in said pressure cell for measuring the pressure of saidprocess circuit communicated through said closed pressure circuit whensaid valve member is in said open position.
 2. The pressure transducerof claim 1 wherein said pressure sensor comprises a pressure membraneextending traversly across said closed pressure circuit at said outlet.3. The pressure transducer of claim 2 wherein said outlet is directlydownstream of said valve member, and said pressure sensor is directlydownstream of said outlet so that minimum dead space is provided betweensaid valve member and said pressure sensor.
 4. The pressure transducerof claim 3 wherein said pressure cell is included in a detachable coverelement mounted to said housing over the outlet of said valve chamber.5. The pressure transducer of claim 4 including an electronics housingmounted to said flow control unit carrying an electronic measuringsystem.
 6. The pressure transducer of claim 5 wherein said electronicshousing is carried by said detachable cover element.
 7. The pressuretransducer of claim 1 including a pair of flow control units eachincluding a closed pressure circuit defined by a valve inlet, a valvechamber, and a valve outlet; each of said closed pressure circuitsextending from said process circuit to a central differential pressurecell containing a differential pressure sensor downstream of said valveoutlet for each of said flow control units.
 8. The pressure transducerof claim 7 wherein each of said closed pressure circuits in said pair offlow control units extends parallel to the other from said processcircuit and are then brought towards each other to end on opposite sidesof said differential pressure sensor at said central differentialpressure cell.
 9. The pressure transducer of claim 8 wherein said paidof flow control units each include separate housing adapted foradjoining to each other in the region of said central differentialpressure cell and are capable of being separated to provide access tosaid central pressure cell.
 10. A pressure transducer assembly formeasuring the pressure in a process circuit of a process plant, saidpressure transducer comprising: a flow control unit having a housingwith a valve chamber; an inlet included in said housing for providingfluid communication between said valve chamber and said process circuit;an outlet included in said housing in fluid communication with saidvalve chamber; a pressure sensor adjacent said outlet opposite saidvalve chamber and extending across said outlet; and, a valve memberincluded in said valve chamber for controlling flow from said processcircuit to said pressure sensor.
 11. The pressure transducer of claim 10including a closed pressure circuit defined from said inlet, valvechamber, and outlet; extending from said process circuit to saidpressure sensor.
 12. The pressure transducer of claim 10 wherein saidvalve member includes a passageway movable between an open position forallowing flow from said inlet of said valve chamber to said outlet ofsaid valve chamber, and a closed position for preventing flow throughsaid valve chamber.
 13. The pressure transducer of claim 10 wherein saidpressure sensor is carried in a pressure cell disposed adjacent saidoutlet of said valve chamber.
 14. The pressure transducer of claim 13wherein said outlet is directly downstream of said valve member, andsaid pressure sensor is directly downstream of said outlet so thatminimum dead space is provided between said valve member and saidpressure sensor.
 15. The pressure transducer of claim 14 wherein saidpressure cell is included in a detachable cover element mounted to saidhousing over the outlet of said valve chamber.
 16. The pressuretransducer of claim 15 including an electronics housing mounted to saidflow control unit carrying an electronic measuring system.
 17. Thepressure transducer of claim 16 wherein said electronics housing iscarried by said detachable cover element.
 18. The pressure transducer ofclaim 17 including a pair of flow control units each including a closedpressure circuit defined by a valve inlet, a valve chamber, and a valveoutlet; each of said closed pressure circuits extending from saidprocess circuit to a central differential pressure cell containing adifferential pressure sensor downstream of said valve outlet for each ofsaid flow control units.
 19. The pressure transducer of claim 18 whereineach of said closed pressure circuits in said pair of flow control unitsextends parallel to the other from said process circuit and are thenbrought towards each other to end on opposite sides of said differentialpressure sensor at said central differential pressure cell.
 20. Thepressure transducer of claim 19 wherein said paid of flow control unitseach include separate housing adapted for adjoining to each other in theregion of said central differential pressure cell and are capable ofbeing separated to provide access to said central pressure cell.